Pneumatic measurement apparatuses are known that use a pressure measurement for determining the distance between a measurement nozzle of the apparatus and a facing wall, said distance itself being representative of the dimension of a part to be monitored. In the most common case, the pneumatic measurement apparatus includes two measurement branches connected to a common feed, with each branch including a measurement chamber fed with gas under pressure via a feed nozzle, an outlet nozzle spaced apart from the feed nozzle, and a pressure take-off point disposed between the feed nozzle and the outlet nozzle. The pressure take-off points in the two outlet branches are connected to a differential pressure gauge, with one of the measurement branches having an outlet nozzle of fixed or adjustable leakage section to serve as a reference branch while the other measurement branch includes a measurement outlet nozzle generating a leakage section that varies as a function of the distance of the object to be measured relative to the measurement outlet nozzle. When the feed pressure is particularly stable, it is possible to make do with only one measurement branch fitted with a measurement outlet nozzle. In either case, it has been observed that in order to perform a pressure measurement without excessive noise, i.e. without the measurement being excessively influenced by disturbances that result from the flow of gas in the measurement chamber and that have no relationship with the distance between the measurement outlet nozzle and the object to be measured, it is necessary to provide a distance between the feed nozzle and the pressure take-off point which is of the order of 30 times to 100 times the diameter of the feed nozzle, i.e. a distance of 42 mm to 140 mm for a commonly-used feed nozzle having a diameter of 1.4 mm. Such a constraint is extremely penalizing from the point of view of the space occupied by the measurement apparatus.
An object of the invention is to provide measurement apparatus that is more compact.